I'm thinking of dropping IE7 in favor of Opera.

Are there any drop dead reasons for not choosing Opera? Other than open architecture, is FireFox better than Opera?

Thanks.

I use Firefox on my PC I use opera on my cell phone. I really can't give you a reason why I do but I like Firefox much better then IE.

Firefox has a much bigger user base which helps with (a) development and (b) website owners making sure that their site works well with FF. I have noticed that Opera users are extremely devoted to their browser.